Communications between individuals have become an important and extensive part of contemporary society. As a result, technology has accelerated in order to produce numerous ways for individuals to communicate with one another. For example, telephone systems have become much more elaborate, facsimile machines have proliferated, computer networks are more extensive and cellular telephone systems are commonplace.
One particularly advantageous communications medium is phone message delivery. In particular, phone message delivery typically includes a system whereby a person may call the system and leave a voice message. Thereafter, the voice message is delivered to a second person who is the intended recipient of the voice message. This type of messaging system permits one person to communicate a voice message to a second person through the convenience of leaving a message without having to speak live or simultaneously with the intended recipient of the message.
One key problem or underlying complication in voice message delivery systems, however, has been an accurate and reliable delivery of the voice message to the intended recipient. In particular, certain voice message systems operate such that a voice message is stored and the intended recipient is later called in order to deliver the message to that person. Once the intended recipient answers the call, the voice message is delivered. As a result, the system must include an accurate subsystem which can detect when the intended recipient, or some answering person, has answered the phone so that the message may be delivered to that person. Thus, this system must be able to distinguish various different types of signals which it may receive in response to its efforts to contact the intended recipient of the voice message. For example, when the system tries to contact the recipient person, it may receive a ring signal, a busy signal, a clicking on the phone line or various other types of signals rather than receiving the voice response of the intended recipient. Accordingly, the subsystem must be able to distinguish these various systems from the voice of the recipient so that the message is not inadvertently delivered when it should not be.
One previous method for detecting a voice signal on the telephone line is based on Fourier analysis. Under this analysis, a telephone system places a telephone call to the intended recipient in order to deliver the voice message. The system monitors the telephone line signals received once the call is placed. In particular, the system observes eight channels of frequency components to determine whether the signals on the line represent a human voice or other possible signals which may be encountered on a telephone line. This method has been developed with the assumption that a human voice has no consistency over several 32 millisecond frames in frequency components, while non-voice signals such as a ring, busy or reorder signal do have consistency. Therefore, after taking a Fourier transform of the incoming signal, a consistency test is performed. Thereafter, based on the analysis of the consistency test, the Fourier prior art system determines whether the received signal is a human voice or some other signal.
The Fourier transform method and process, however, have been shown to perform poorly, particularly when the incoming signal has substandard quality associated with it. For example, for older telephone exchange systems, various static or clicks on the system may cause erroneous analysis under the Fourier transform system. As another example, even though there are specifications for ring signals from the Bell Telephone System, ring signals frequently violate the specifications. As a consequence, the existing Fourier method often misclassifies a ring signal as a human voice, or vice versa. In the instance where a ring signal is misinterpreted as a human voice, the system may attempt to deliver the voice message when in fact there is no human at the receiving end of the line to receive it. Naturally, this erroneous delivery prevents the actual intended recipient from ever receiving the message and, therefore, may have devastating consequences.
From the above, it may be appreciated that a need has risen for a telephone signal classification and phone message delivery system which corrects the problems or substantially reduces those associated with prior art systems.